1. Field of the Invention
The present invention relates to a battery module constituted by connecting a plurality of cells so as to obtain a necessary power capacity.
2. Description of Related Art
FIG. 9 shows a conventional battery module made by connecting a plurality of rechargeable batteries and coupling them together as one so as to obtain the necessary power. In this battery module, a plurality of cells 31 (31a to 31j) made of sealed alkaline rechargeable batteries as shown in FIG. 10 are arranged side by side, with the long lateral walls of their battery cases 32 adjacent each other. End plates 42 are arranged against the outside of the cells 31a and 31j at both ends, and the group of batteries and the two end plates 42 are bound together with binding bands 43 so as to couple the cells together as one piece.
For the cells 31, an electrode plate group 37, comprising positive electrode plates and negative electrode plates layered with intervening separators, thereby constituting elements for electromotive force, is accommodated in a battery case 32 together with a liquid electrolyte, and the open end of the battery case 32 is closed with a lid 36 provided with a safety vent 35. From the upper end at one side of the positive electrode plates forming the electrode plate group 37, leads 39 extend upward and are connected to a positive electrode terminal 33 above them, and similarly, from the upper end of the other side of the negative electrode plates, leads 39 extend upward and are connected to an negative electrode terminal 34 above them. The positive electrode terminal 33 and the negative electrode terminal 34 are attached to the lid 36.
The positive electrode terminals 33 and negative electrode terminals 34 of coupled neighboring cells 31 are connected by connection plates 41, thereby connecting all cells 31 in series. When the battery cases 32 are coupled, ribs 38, which protrude vertically from the long lateral walls of the battery cases 32, are abutted against each other, forming coolant passages running in the vertical direction along the long lateral walls of the battery cases 32 in the space between ribs 38. The cells 31a to 31j are cooled by flowing air through these coolant passages.
With the configuration of this conventional battery module, individual cells 31 are arranged in parallel, with the ribs 38 on the long lateral walls of the cell cases 32 being abutted each other. While each of the cells 31 can be cooled substantially uniformly by the coolant passages formed between the ribs 38 on one hand, the entire battery module cannot be made compact by the space provided for the coolant passages on the other hand.
If the pitch space between adjacent ribs 38 is made smaller, the cross-sectional area of the coolant passages formed between the ribs 38 become smaller, and the cooling performance will decrease accordingly. Conversely, if the ribs 38 area arranged at a wider pitch space, the walls of each cell case 32 will more easily expand outwards by the internal pressure of each cell 31, whereby the cross-sectional area of the coolant passages will become smaller and the cooling performance will deteriorate. On the other hand, if the walls of the cell cases 32 are made thicker as the countermeasure against the internal pressure of the cells, heat conductivity will deteriorate, and the cooling performance will anyway deteriorate.
In view of these problems of the prior art, it is an object of the present invention to provide a battery module of a compact structure, in which each of the cells constituting the battery module can be uniformly cooled highly efficiently.
To achieve the above object, a battery module according to the present invention comprises:
a plurality of prismatic cell cases having short lateral walls and long lateral walls arranged side by side, with adjacent short lateral walls being integral with each other; and
a single lid member for integrally closing upper open ends of the plurality of prismatic cell cases, wherein
each of the cell cases accommodates therein a group of electrodes comprising a group of positive electrode plates and a group of negative electrode plates stacked alternately upon one another parallel to the long lateral walls of the cell cases with intervening separators therebetween, thereby constituting rechargeable batteries respectively, and
neighboring rechargeable batteries are connected in series at their opposite lateral ends with each other.
Since neighboring cell cases share their short lateral walls, and no cooling space is provided between the cells, the battery module can be made compact as a whole. Further, since each of the cells accommodates therein a group of electrode plates stacked parallel to the long lateral walls of the cell cases, and the neighboring cells are mutually connected in series at the opposite ends of the long lateral walls, the cells can be connected together compactly. Moreover, the battery module is cooled as a whole along the long lateral walls of the integral battery case formed as one continuous plane, so that each of cells constituting the battery module is uniformly and efficiently cooled.
Other and further objects, features and advantages of the invention will appear more fully from the following description.